Key highlights
- The article underscores that simply sharing a physical Ethernet-APL layer does not guarantee device interoperability across different fieldbus protocols.
- It highlights Ethernet-APL’s primary benefit: delivering fast, Ethernet-class communications (10 Mbps) safely into hazardous areas.
We presented Control’s cover article on the Open Process Automation Standard (O-PAS) in March, but its quest for plug-and-play interoperability got tattooed on my brain. So, I kept asking about it when interviewing for this month’s “Ethernet-Advanced Physical Layer (APL) bears fruit” feature article.
To their credit, most sources acknowledge that being on the same Ethernet or APL physical layer won’t allow direct interoperability by devices running different fieldbus protocols, such as Profinet, EtherNet/IP, HART-IP, Foundation Fieldbus HSE, Modbus TCP/IP and several others.
This is more honest than some former sources, who used to claim or strongly imply that just being on Ethernet conferred interoperability on all participants. This isn’t true because simply getting some devices on the same wire doesn’t mean the protocols they’re using can talk to each other, just as getting everyone on the same telephone line doesn’t suddenly guarantee they can all speak the same language.
Now that’s cleared up again, Ethernet-APL’s primary goal is to get faster, Ethernet-based, IT-style communications and capabilities safely into hazardous environments, and APL moves extremely fast compared to traditional 4-20 mA or fieldbus communications. Ethernet-APL runs at 10 Mbps, which is 320 times faster than protocols like Foundation Fieldbus or Profibus PA that operate at 31.25 kbps or HART that runs at 1,200 bps.
APL’s speed and bandwidth are already turning up multiple expected benefits, such as handling greater volumes and varieties of data from more diverse types of sensors and instruments, where information used to be stranded because it had no place to go. However, APL is also assisting in several unanticipated areas, such as simplifying and speeding up formerly time-consuming configuration and other tasks.
One source reported that APL field switches can take in data using one protocol, and use their internal data processing to send out contents or analyses using another protocol. Many gateways and switches already perform similar data conversions or protocol translations, so maybe APL can take over some of these jobs?
I remember arguing against allowing Blue Bunny’s use of radio frequency identification (RFID) tags on two-gallon packages of ice cream into a long-ago wireless article because I thought they were just doing documentation. They weren’t directly measuring or transmitting temperatures, but the time and location confirmed by those RFID tags was an indirect but sufficient guarantee that the ice cream in those buckets was flash frozen.
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This is why I believe when the entrance to an innovation or other endeavor is blocked, pressure builds on other metaphorical access points until one bursts, entry is gained, and the goal is achieved indirectly. It's just like in the Sound of Music, when Julie Andrews says, “When the Lord closes a door, somewhere He opens a window.”
I think APL may doing something similar. While it doesn’t achieve actual interoperability, it’s speed and bandwidth may get many sought-after jobs done anyway. And, the faster it gets tasks done, the more similar to interoperability they’ll probably appear.
Of course, APL also leans heavily on the OPC UA information sharing strategy, and the OPC Foundation is one of APL’s four founding, standards development organizations. Likewise, OPC UA is also the networking cornerstone of the O-PAS connectivity framework (OCF). So, isn’t it conceivable that APL could help O-PAS get into hazardous areas?
If I’m full of it and completely clueless, please let me know. Unlike many in this modern age, I’d welcome evidence to the contrary because it would likely be a good story.
